Process and plant for producing tyres for vehicle wheels

ABSTRACT

A plant and a process for producing tires wherein the process includes the steps of: a) building a green tire on a toroidal support in a building line of a tire production plant; b) transferring the green tire and the relevant toroidal support from the building line of the production plant to a first holding unit; c) transferring the green tire and the relevant toroidal support from the first holding unit to a vulcanization line of the production plant; d) molding and vulcanization the green tire in the vulcanization line of the production plant; e) separating the molded and vulcanized tire from the relevant toroidal support; f) transferring the toroidal support, separated from the relevant tire, from the vulcanization line to the first holding unit; and g) transferring the toroidal support, separated from the relevant tire, from the first holding unit to the building line of the production plant, wherein steps b) and g) are carried out through a first transfer device and steps c) and f) are carried out through a second transfer device different from the first transfer device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 12/312,437,filed May 11, 2009, which is a national phase application based onPCT/IB2006/004036, filed Nov. 27, 2006, the content of both of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a process for producing tyres forvehicle wheels.

In particular, the present invention relates to a process for producingtyres built on a toroidal support.

Another object of the invention is a plant for producing tyres forvehicle wheels, able to be used to carry out the aforementionedproducing process.

Description of the Related Art

The production cycles of a tyre provide that, after a building processin which the various components of the same tyre are made and/orassembled in a building line, a vulcanization and moulding process iscarried out, in a suitable vulcanization line, adapted for defining thestructure of the tyre according to a desired geometry and tread pattern.

A tyre generally comprises a toroidally ring-shaped carcass includingone or more carcass plies, strengthened with reinforcing cords, lying insubstantially radial planes, (a radial plane contains the rotation axisof the tyre). Each carcass ply has its ends integrally associated withat least one metal reinforcing annular structure, usually known as beadcore, constituting the reinforcing at the beads, i.e. at the radiallyinternal ends of the tyre, the function of which is to enable assemblingof the tyre with a corresponding mounting rim. Placed crown wise to saidcarcass is a band of elastomer material, called tread band, in which, atthe end of the vulcanization and molding steps, a raised pattern isformed for ground contact. A reinforcing structure usually known as beltstructure is placed between the carcass and the tread band. In the caseof car tyres, this structure usually comprises at least two radiallysuperposed strips of rubberised fabric provided with reinforcing cords,generally of metal material, positioned parallel to each other in eachstrip and in a crossed relationship with the cords of the adjacent strippreferably symmetrically arranged with respect to the equatorial planeof the tyre. Preferably said belt structure further comprises at aradially external position thereof, at least on the ends of theunderlying belt strips, also a third layer of textile or metallic cords,circumferentially disposed (at zero degrees).

Finally, in tyres of the tubeless type, i.e. devoid of an air tube, aradially internal layer, called liner, is present which hasimperviousness features to ensure the air-tightness of the tyre.

To the aims of the present description as well as in the followingclaims, by the term “elastomer material” it is intended a compositioncomprising at least one elastomer polymer and at least one reinforcingfiller. Preferably this composition further comprises additives such ascross-linking and/or plasticizing agents. By virtue of the cross-linkingagents, this material can be cross-linked through heating so as to formthe final manufactured article.

In recent times tyre production processes in which a green tyre is builton a rigid toroidal support has been introduced in the field. Saidprocesses are preferably used for tyres produced starting from a limitednumber of elementary semifinished products fed onto a toroidal supportwhose outer profile coincides with that of the radially internal surfaceof the tyre that is wished to be produced. The toroidal support ismoved, preferably by means of a robotized system, among a plurality ofworking stations in each of which, through automated sequences, aparticular building step of the tyre is carried out. At the end of thebuilding steps, the toroidal support with the tyre supported thereby isarranged inside, a vulcanization mould.

In the present context, by the term “green tyre” a tyre obtained by thebuilding process is indicated.

An example of the aforementioned processes is described in WO 01/32409,in the name of the same Applicant, which illustrates a tyre buildingline provided with working stations, each arranged to make and assembleat least one structural component of the tyre being processed, in whichat least one series of tyres comprising at least a first and a secondtyre model that are different from each other is treated simultaneously,and in which the transferral of the tyres to the vulcanization line iscarried out through robotized arms and according to a transferring ratewhich is equal to the transferring rate of the tyres to each of saidworking stations.

WO 01/39963, in the name of the same Applicant, on the other hand,illustrates a process for producing tyres that are different from eachother, comprising a building unit having a plurality of workingstations, each adapted for assembling at least one structural componenton at least one type of tyre being processed, a vulcanization unit, anda device for transferring and moving the tyre being processed, operatingbetween the working stations and the vulcanization unit.

Said device for transferring and moving the tyre transfers a green tyreto the vulcanization unit; after vulcanization, it picks up a vulcanizedand moulded tyre from the vulcanization unit and transfers it to thefirst working station of the building unit, where the tyre is removedfrom the corresponding toroidal support. The latter is then transferredfrom the same device for transferring and moving the tyre into atemperature stabilizing device. In the case in which the tyre to beproduced requires a different type of toroidal support, the device picksup the suitable toroidal support from a feeding station and inserts itinto the temperature stabilizing device.

The Applicant has noted that since the aforementioned device fortransferring and moving the tyre is arranged to carry out numerousoperations and to make large displacements, requires large manoeuvringspaces and therefore a plant of considerable size. In particular WO01/39963 describes the use of a robotized arm translating on a rail, asa device for transferring and moving the tyre.

The Applicant has also verified that, in such known processes, anyanomaly or malfunctioning in any one from the vulcanization unit,mounting/dismounting unit of the toroidal supports, and temperaturestabilizing unit, has the immediate consequence of blocking theproduction plant with serious repercussions on its productivity.

For example, in the case of blocking of the mounting/dismounting unit ofthe toroidal support, the device for transferring and moving the tyredoes not carry out the removal of the tyre from the vulcanizer, even ifthe vulcanization has been completed. Consequently, the tyre obtainedbecomes overvulcanized and therefore is not in accordance with therequired specifications.

SUMMARY OF THE INVENTION

The Applicant has observed that by equally distributing the duties ofthe active transfer devices between the building line and thevulcanization line, it is possible to obtain a more flexible process forproducing tyres, in which possible anomalies or malfunctions do notaffect productivity.

The Applicant has thus realised that by rationalising the workload ofthe devices adapted for transferring the toroidal supports between thebuilding line and the vulcanization line, and within the two linesthemselves, it is possible to absorb said anomalies or malfunctionswithout consequences on the rest of the plant.

The Applicant has therefore found that by suitably managing saidtransfer devices, both in terms of the number and the type of operationsthat each of them has to carry out, it is possible to obtain a processfor producing tyres that allows to avoid wastes in case of failure,slowing down of the same producing process, as well as to reduce thesize of the same production plant.

In accordance with a first aspect thereof, the invention concerns aprocess for producing tyres for vehicle wheels comprising the steps of:

a) building a green tyre on a toroidal support in a building line of atyre production plant;

b) transferring the green tyre and the relevant toroidal support fromthe building line of the production plant to a first holding unit;

c) transferring the green tyre and the relevant toroidal support fromthe fast holding unit to a vulcanization line of the production plant;

d) moulding and vulcanizing the green tyre in the vulcanization line ofthe production plant;

e) separating the moulded and vulcanized tyre from the relevant toroidalsupport;

f) transferring the toroidal support, separated from the relevant tyre,from the vulcanization line to the first holding unit;

g) transferring said toroidal support, separated from the relevant tyre,from the first holding unit to the building line of the productionplant;

in which said steps b) and g) are carried out through a first transferdevice and said steps c) and f) are carried out through a secondtransfer device different from said first transfer device.

According to a preferred embodiment, said step c) of transferring thegreen tyre and the relevant toroidal support from the first holding unitto the vulcanization line of the production plant comprises step c1) oftransferring the green tyre and the relevant toroidal support from thefirst holding unit to at least one vulcanization unit of thevulcanization line of the production plant through the second transferdevice.

Advantageously, the process for producing tyres for vehicle wheels alsocomprises step f1) of transferring the moulded and vulcanized tyre andthe relevant toroidal support from the vulcanization unit to anmounting/dismounting unit of the vulcanization line through said secondtransfer device.

Preferably, in this case, said step f) of transferring the toroidalsupport, separated from the relevant tyre, from the vulcanization lineto the first holding unit comprises step f2) of transferring thetoroidal support, separated from the relevant tyre, from themounting/dismounting unit of the vulcanization line to the first holdingunit through said second transfer device.

Preferably, said step g) of transferring the toroidal support, separatedfrom the relevant tyre, from the first holding unit to the building linecomprises step g1) of transferring the toroidal support, separated fromthe relevant tyre, from the first holding unit to a cooling unit of thebuilding line through said first transfer device.

Advantageously, said step g) also comprises step g2) of transferring thetoroidal support, separated from the relevant tyre, from the firstholding unit to a working station of the building line of the productionplant through said first transfer device.

Advantageously, said step f1) of transferring the moulded tyre andvulcanized and the relevant toroidal support from the vulcanization unitto the mounting/dismounting unit comprises the substeps of:

f1′) transferring the moulded and vulcanized tyre and the relevanttoroidal support from the vulcanization unit to the first holding unit;and

f1″) transferring the moulded and vulcanized tyre and the relevanttoroidal support from the first holding unit to the mounting/dismountingunit.

Preferably, said step b) of transferring the green tyre and the relevanttoroidal support from the building line to the first holding unitcomprises the substeps of:

b1) transferring the green tyre and the relevant toroidal support fromthe building line to a second holding unit; and

b2) transferring the green tyre and the relevant toroidal support fromsaid second holding unit to the first holding unit.

Advantageously, said step g) of transferring the toroidal support,separated from the relevant tyre, from the first holding unit to thebuilding line comprises the substeps of:

g′) transferring the toroidal support, separated from the relevant tyre,from the first holding unit to a second holding unit; and

g″) transferring the toroidal support, separated from the relevant tyre,from said second holding unit to the building line.

Preferably step g″) comprises the step of transferring the toroidalsupport, separated from the relevant tyre, from the second holding unitto a working station of the building line.

The Applicant has also realised that it is possible to improveproduction by providing, before the moulding and vulcanization step, apre-heating step of at least one mould of the correspondingvulcanization unit.

In accordance with a second aspect thereof, the invention concerns aplant for producing tyres for vehicle wheels comprising:

-   -   a building line of a green tyre on a respective toroidal        support;    -   a vulcanization line of the tyre;    -   a first holding unit operatively arranged between said building        line and said vulcanization line;    -   a first transfer device to transfer said toroidal support from        said first holding unit to said building line and vice-versa;    -   a second transfer device to transfer said toroidal support said        first holding unit to said vulcanization line and vice-versa.

In the tyre production plant, according to a preferred embodiment, thebuilding line of the green tyre comprises:

-   -   a plurality of working stations for building the green tyre; and    -   at least one cooling unit of a toroidal support, separated from        the relevant tyre.

According to a further preferred embodiment, the vulcanization line ofthe tyre comprises:

-   -   at least one vulcanization unit of the tyre; and    -   at least one mounting/dismounting unit of a toroidal support.

Preferably, said first transfer device is adapted for:

-   -   transferring the green tyre and the respective toroidal support        from the building line of the production plant to the first        holding unit;    -   transferring the toroidal support, separated from the respective        tyre, from the first holding unit to the cooling unit of the        building line; and    -   transferring the toroidal support, separated from the respective        tyre, from the cooling unit of the building line to a working        station of the building line.

According to a different preferred embodiment, the tyre production plantalso comprises a second holding unit adapted for holding the green tyreand the relevant toroidal support coming out from the building line andfor holding the toroidal support, separated from the relevant tyre,coming out from the vulcanization line.

In this case, said first transfer device is adapted for:

-   -   transferring the green tyre and the relevant toroidal support        from said second holding unit to the first holding unit;    -   transferring the toroidal support, separated from the relevant        tyre, from the first holding unit to the cooling unit of the        building line of the production plant; and    -   transferring the toroidal support, separated from the respective        tyre, from the cooling unit of the building line to the second        holding unit.

Preferably, said second transfer device is adapted for:

-   -   transferring the green tyre and the relevant toroidal support        from the first holding unit to at least one vulcanization unit        of the vulcanization line of the production plant;    -   transferring the moulded and vulcanized tyre and the relevant        toroidal support from the vulcanization unit to the        mounting/dismounting unit of the vulcanization line of the        production plant; and    -   transferring the toroidal support, separated from the relevant        tyre, from the mounting/dismounting unit of the vulcanization        line to the first holding unit.

The Applicant has also noted that it is possible to improve theproductivity of the tyre production plant by providing a vulcanizationline comprising two vulcanization units.

Even more preferably, each of said vulcanization units is provided withsix vulcanization moulds. In this way, since the daily productionrequired of a plant of the type described in the present context isequal to about 500 covers per day, it is possible to carry out 50 cyclesper day and have 2 vulcanization moulds free for each cycle. Such feemoulds can advantageously be used for mould changing operations,required by the vulcanization unit, and to pre-heat at least one mouldinserted in the vulcanization unit.

In a variant of the present invention, the production plant comprisestwo mounting/dismounting units and/or four cooling units of the toroidalsupports.

Advantageously, the production plant also comprises at least one rail anwhich at least one from said first transfer device and said secondtransfer device is movable.

In a preferred embodiment of the aforementioned production plant, saidat least one rail extends between at least two units selected from thevulcanization unit, the mounting/dismounting unit, the cooling unit andthe second holding unit and/or from a working station of the buildingline and a unit selected from the vulcanization unit, themounting/dismounting unit, the cooling unit and the second holding unit.

Advantageously, at least one pair of rails constitute a track on whichthe first transfer device and the second transfer device run.

According to an embodiment of the present invention, the tyre productionplant also comprising driving devices to move the first transfer deviceand the second transfer device along said at least one rail.

According to a preferred embodiment of the present invention, at leastone from said first transfer device and said second transfer device is arobotized arm.

Advantageously, said first holding unit comprises at least two seats forhousing the toroidal supports.

Preferably, the first holding unit comprises at least four seats forhousing the toroidal supports.

According to an alternative embodiment of the present invention, saidfirst holding unit is movable and, preferably, along said at least onerail.

In any case, it is possible to design that the first holding unit ispreferably arranged on the track on which the first transfer device andthe second transfer device run.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention shall becomeclear from the following description of some preferred examples ofprocesses and plants for producing tyres according to the invention,made—for indicating and not limiting purposes—with reference to theattached drawings, in which:

FIG. 1 shows a schematic lay-out of a plant for producing tyres forvehicle wheels in which the process according to the present inventionis carried out;

FIG. 2 shows a schematic plan view of a plant for producing tyres forvehicle wheels according to a first embodiment of the invention during astep of the subject process;

FIG. 3 shows a schematic plan view of a plant for producing tyres forvehicle wheels according to a second embodiment of the invention duringa step of the subject process; and

FIGS. 4 and 5 show two partial plan views of a plant for producing tyresfor vehicle wheels.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1-3 a plant for producing tyres for vehiclewheels according to the present invention through which the productionprocess according to the present invention is carried out is generallyindicated with 1.

The plant 1 comprises a building line 2, in which each tyre is built byassembling structural components according to a predetermined sequence,and a vulcanization line 3, in which each green tyre is moulded andvulcanized, within a respective vulcanization mould, thus transformingitself into the finished product.

The building line 2 comprises a plurality of working stations 10preferably arranged along a closed loop path indicatively represented bythe arrows 11 in FIG. 1.

Preferably, said working stations 10 operate simultaneously with eachother, each on at least one tyre, to assemble at least one of itsstructural components thereon.

It should be noted that in the present description and in the subsequentclaims by “structural component” of the tyre it is meant any componentselected for example from: liner, sub-liner, carcass ply/plies, sub-beltinsert, belt strips either crossing over one another or at zero degrees,attachment sheets for the tread band, tread band, rim, bead filler,textile or metallic reinforcement inserts, anti-abrasion insert, or anyportion thereof.

In particular, during the assembly step the various structuralcomponents used in making each tyre are advantageously engaged on atoroidal support the shape of which substantially reproduces theinternal configuration of the tyre to be obtained. Such a toroidalsupport is preferably of the type that is collapsible or dismountableinto a plurality of sectors, as for example described in document WO01/62481 to the Applicant, so as to be able to be easily removed fromthe tyre when processing is completed.

Transfer devices 12 operate in the building line 2 to transfer each ofthe tyres being processed associated with a respective toroidal supportsequentially from one of the working stations 10 to the next workingstation, so as to determine the sequentially assembly of all thecomponents of the tyre.

Preferably, such transfer devices 12 comprise one or more robotized armsassociated with at least one of the working stations 10 and operating onthe individual toroidal supports to carry out the transfer in sequenceof each tyre being processed.

The building line 2 comprises, preferably, at least one cooling unit 6of a toroidal support adapted for carrying a toroidal support coming outfrom the vulcanization line 3 at the suitable temperature to begin a newbuilding process of a green tyre.

A first holding unit 7 of a toroidal support associated with orseparated from a respective tyre being processed is operatively arrangedbetween the building line 2 and the vulcanization line 3 of theproduction plant 1 so as to create a buffer between the two lines.

The production plant 1, according to the present invention, is alsoprovided with a first transfer device R1, to transfer said toroidalsupport associated with or separated from a respective tyre beingprocessed, between the first holding unit 7 and the building line 2, andwith a second transfer device R2, to transfer said toroidal supportbetween the first holding unit 7 and the vulcanization line 3.

Preferably at least one from said first transfer device R1 and saidsecond transfer device R2 comprises a robotized arm.

Preferably, at least one from said first transfer device R1 and saidsecond transfer device R2 is movable on at least one rail 9.

The vulcanization line 3 comprises at least one vulcanization unit 4 ofthe green tyre, and at least one mounting/dismounting unit 5 in whichthe vulcanized and moulded tyre is separated from the respectivetoroidal support.

in the first embodiment of the production plant 1, shown in FIG. 2, thevulcanization line 3 comprises a vulcanization unit 4 and anmounting/dismounting unit 5.

In the second embodiment of the production plant 1, shown in FIG. 3, thevulcanization line 3 comprises two vulcanization unit 4 and anmounting/dismounting unit 5.

Each vulcanization unit 4 comprises a number of vulcanization mouldsadapted for the production capacities of the production plant 1. Inparticular, in the embodiments shown in FIGS. 2-5, each vulcanizationunit 4 comprises six vulcanization moulds.

Preferably, the vulcanization moulds are mounted on a turntable to bedriven in rotation so as to make the same vulcanization moulds carry outa closed-loop path, sequentially carrying them, one after the other, toa tyre loading/unloading station, each associated with its own toroidalsupport.

In this way, a green tyre, after having been loaded into a vulcanizationmould, is subjected to a moulding and vulcanization process and, oncethe suitable time to complete the moulding and vulcanization operationshas been achieved, is unloaded from the mould at the sameloading/unloading station through rotation of the turntable.

The vulcanization moulds are preferably sealed airtight and are arrangedto house a tyre being processed previously built on a toroidal support,the outer surface of which substantially reproduces the internalconfiguration of the tyre to be obtained. Said vulcanization moulds areprovided with working fluid passage devices as illustrated for examplein WO 2004/045837, in the name of the same Applicant.

The mounting/dismounting unit 5 is adapted for housing a vulcanized tyreand the respective toroidal support to perform the separation operationof the vulcanized tyre. In the present context, by the term “separationoperation” it is meant to indicate at least all of the dismountingoperations of the toroidal support, and the removal of the tyre from theaforementioned dismounted toroidal support.

In accordance with an embodiment of the present invention, the firsttransfer device R1 is adapted for:

-   -   transferring the green tyre and the respective toroidal support        from the building line 2 of the production plant 1 to the first        holding unit 7;    -   transferring the toroidal support, separated from the respective        tyre, from the first holding unit 7 to the cooling unit 6 of the        building line 2; and    -   transferring the toroidal support, previously separated from the        respective tyre, from the cooling unit 6 of the building line 2        to a working station 10 of the building line 2.

In accordance with the two embodiments shown in FIGS. 2 and 3, theproduction plant 1 also comprises a second holding unit 8 adapted forholding the green tyre and the relevant toroidal support coming out fromthe building line 2 and for holding the toroidal support, separated fromthe relevant tyre, coming out from the vulcanization line 3.

In this case, the tyre going into the vulcanization line 3 does not comedirectly from a station 10 of the building line, but transits throughsaid second holding unit 8 and therefore, in this case, the firsttransfer device R1 is adapted for:

-   -   transferring the green tyre and the relevant toroidal support        from said second holding unit 8 to the first holding unit 7;    -   transferring the toroidal support, separated from the relevant        tyre, from the first holding unit 7 to the cooling unit 6 of the        building line 2; and    -   transferring the toroidal support, separated from the respective        tyre, from the cooling unit 6 of the building line 2 to the        second holding unit 8.

Independently from whether said second holding unit 8 is present, thesecond transfer device R2 is preferably adapted for:

-   -   transferring the green tyre and the relevant toroidal support        from the first holding unit 7 to a vulcanization unit 4 of the        vulcanization line 3 of the production plant 1;    -   transferring the moulded and vulcanized tyre and the relevant        toroidal support from the vulcanization unit 4 to the        mounting/dismounting unit 5 of the vulcanization line 3 of the        production plant 1; and    -   transferring the toroidal support, separated from the relevant        tyre, from the mounting/dismounting unit 5 of the vulcanization        line 3 to the first holding unit 7.

As illustrated above, said first and second transfer devices R1 and R2can advantageously be movable on at least one rail 9. In the embodimentillustrated in FIGS. 2 and 3, at least one pair of rails 9 constitutesas track on which the aforementioned transfer devices R1 and R2 arecapable of moving (in the case illustrated, by translating).

Advantageously, said rails 9 preferably extend between at least twounits from the vulcanization unit 4, the mounting/dismounting unit 5,the cooling unit 6 and the second holding unit 8 and/or between aworking station 10 of the building line 2 and at least one unit from thevulcanization unit 4, the mounting/dismounting unit 5, the cooling unit6 and the second holding unit 8.

In the case in which the production plant 1 is provided with a secondholding unit 8, said rails 9 also extend between the cooling unit 6 andsaid second holding unit 8.

Advantageously, the first holding unit 7 comprises at least two seatsfor housing the toroidal supports respectively associated with and/orseparated from a green or moulded and vulcanized tyre.

According to the embodiments shown in FIGS. 2-5, said first holding unit7 comprises four seats for housing the toroidal supports.

In such embodiments, the first holding unit 7 is arranged on the rail onwhich the first transfer device R1 and the second transfer device R2run.

According to a variant of the present invention, the first holding unit7 is movable so as to assist the transfer of the first transfer deviceR1 and of the second transfer device R2 simplifying their manoeuvres andshortening the distances that they have to accomplish.

In this ease, the first holding unit 7 is advantageously movable alongsaid rails 9.

In accordance with an embodiment, the production plant 1 comprisesdriving devices to move the first transfer device R1 and the secondtransfer device R2 along said rails 9. Said driving devices can beassociated with the rails 9 or else with the first transfer device R1and with the second transfer device R2.

Where the productions requirements are such, it is possible to providethe vulcanization line 3 with two mounting/dismounting units 5 and/orthe building line 2 with four cooling units 6.

With reference to the production plant 1 illustrated in FIGS. 1-5, apreferred embodiment of a production process according to the inventionwill now be described.

In accordance with a first step a), a green tyre is built on arespective toroidal support by assembling each structural component ofthe tyre according to a predetermined sequence at the aforementionedworking stations 10 of the building line 2 of the production plant 1.

This building step of each tyre is carried out for example according tomethods illustrated in document WO 01/32409, to the same Applicant.

When the building step is complete, the process for producing tyresaccording to the present invention provides carrying out a step b) oftransferring the green tyre and the relevant toroidal support from thebuilding line 2 of the production plant 1 to the first holding unit 7.Such a step b) is carried out through the first transfer device R1.

The next step c) provides transferring the green tyre and the relevanttoroidal support from the first holding unit 7 to the vulcanization line3 through the second transfer device R2, different to the first transferdevice R1.

Thereafter the green tyre is moulded and vulcanized in the vulcanizationline 3 of the production plant 1 so as to define the structure of thetyre according to the desired geometry and tread pattern.

Once vulcanized and moulded, the tyre is separated from the relevanttoroidal support in a step e) that comprises the dismounting of thetoroidal support and the removal of the moulded and vulcanized tyre fromsaid toroidal support. Preferably said step e) also comprises thesubsequent remounting of the toroidal support, which is thus ready foranother production cycle.

At this point the toroidal support, separated from the relevant tyre, issubjected to step f) of transferral from the vulcanization line 3 to thefirst holding unit 7 through the second transfer device R2.

Thereafter, the first transfer device R1 carries out step g) oftransferring the toroidal support, from the first holding unit 7 to thebuilding line 2 of the production plant 1.

Preferably, step c) of transferring the green tyre and the relevanttoroidal support from the first holding unit 7 to the vulcanization line3 of the production plant 1 comprises step c1) of transferring the greentyre and the relevant toroidal support from the first holding unit 7 toa vulcanization unit 4 of the vulcanization line 3 through the secondtransfer device R2.

Advantageously, the process according to the present invention,comprises the further step f1) of transferring the tyre, after it hasbeen moulded and vulcanized, and the relevant toroidal support from thevulcanization unit 4 to the mounting dismounting unit 5 of thevulcanization line 3 through said second transfer device R2.

In this case, said step f) of transferring the toroidal support,separated from the relevant tyre in the mounting/dismounting station 5,from the vulcanization line 3 to the first holding unit 7 comprises stepf2) of transferring the toroidal support, after it has been separatedfrom the relevant tyre, from the mounting/dismounting unit 5 of thevulcanization line 3 to the first holding unit 7 through said secondtransfer device R2.

Preferably, step g) of transferring the toroidal support separated fromthe relevant tyre from the first holding unit 7 to the building line 2comprises step g1) of transferring the toroidal support from the firstholding unit 7 to the cooling unit 6 through the first transfer deviceR1.

Said step g) also comprises a step g2) of transferring the toroidalsupport from said cooling unit 6 to a working station 10 of the buildingline 2 through the first transfer device R1.

According to an alternative embodiment of the process for producingtyres, step f1) of transferring the vulcanized and moulded tyre and therelevant toroidal support from the vulcanization unit 4 to themounting/dismounting unit 5 comprises the substeps of:

f1′) transferring the vulcanized and moulded tyre and the relevanttoroidal support from the vulcanization unit 4 to the first holding unit7; and

f1″) transferring the vulcanized and moulded tyre and the relevanttoroidal support from the first holding unit 7 to themounting/dismounting unit 5.

In other words, according to such an alternative embodiment, thetoroidal support transits by the first holding unit 7 even after thevulcanization process, before the toroidal support has been dismountedand, after the removal of the vulcanized tyre, mounted again.

Preferably, step b) of transferring the green tyre and the relevanttoroidal support from the building line 2 to the first holding unit 7comprises the substeps of:

b1) transferring the green tyre and the relevant toroidal support fromthe building line 2 to a second holding unit 8; and

b2) transferring the green tyre and the relevant toroidal support fromsaid second holding unit 8 to the first holding unit 7.

In a similar manner, step g) of transferring the toroidal support,separated from the relevant tyre, from the first holding unit 7 to thebuilding line 2 comprises the substeps of:

g′) transferring the toroidal support from the cooling unit 6 to thesecond holding unit 8; and

g″) transferring the toroidal support from said second holding unit 8 tothe building line 2.

Preferably step g″) comprises the step of transferring the toroidalsupport from said second holding unit 8 to a working station 10 of thebuilding line 2.

According to an embodiment, the process for producing tyres for vehiclewheels comprises, before step d) of moulding and vulcanizing the tyre inthe vulcanization unit 4, a pre-beating step of a mould of thecorresponding vulcanization unit 4.

FIG. 4 schematically shows the transferrals carried out by the firsttransfer device R1, in an embodiment of the present invention. Suchtransferrals are indicated by the arrows F1, F5 and F6.

Similarly, FIG. 5 schematically shows the transferrals carried out bythe second transfer device R2, in the same embodiment. Thesetransferrals are indicated by the arrows F2, F3 and F4.

The steps of the production process according to the present inventionhave up to now been described in sequence from the building of the greentyre up to the vulcanized tyre leaving the production plant. However,the steps of the process occur simultaneously and the units such as thevulcanization unit 4, the mounting/dismounting unit 5, the cooling unit6 and the second holding unit 8, operate simultaneously, each on atleast one tyre to carry out the step of the production process on it forwhich it is intended.

In order to better understand the invention, with reference to FIGS. 4and 5, it is possible to schematize the production process according toa possible embodiment of the present invention, in normal operatingconditions, i.e. when the vulcanization unit 4 is full, as follows.

The second transfer device R2 in sequence carries out the steps of:

F3) transferring the moulded tyre and vulcanized and the relevanttoroidal support from the vulcanization unit 4 to themounting/dismounting unit 5;

F2) transferring the green tyre and the relevant toroidal support fromthe first holding unit 7 to a vulcanization unit 4;

F4) transferring the toroidal support, separated from the relevant tyre,from the mounting/dismounting unit 5 to the first holding unit 7.

At the same time, the first transfer device R1 in sequence carries outthe steps of:

F1) transferring the green tyre and the relevant toroidal support from astation 10 of the building line 2 to the first holding unit 7;

F6) transferring the toroidal support, separated from the relevant tyre,from the cooling unit 6 to a working station 10 of the building line 2;

F5) transferring the toroidal support, separated from the relevant tyre,from the first holding unit 7 to the cooling unit 6.

Preferably, F1) and F2) are carried out simultaneously, just as F6) iscarried out simultaneously to F4) and F5) is carried out simultaneouslyto F4.

The invention claimed is:
 1. A plant for producing one or more tyres forvehicle wheels comprising: a building line, for a green tyre on atoroidal support, comprising: a plurality of work stations for buildingthe green tyre; and a cooler for said toroidal support; a vulcanizationline for the tyre comprising: a vulcanization unit for the tyre; and amounter/dismounter for said toroidal support; a first holding unitoperatively arranged between said building line and said vulcanizationline; a first transfer device to transfer said toroidal support fromsaid first holding unit to said building line and vice-versa and saidfirst transfer device comprising a robotized arm; a second transferdevice to transfer said toroidal support from said first holding unit tosaid vulcanization line and vice-versa and said second transfer devicecomprising a robotized arm; and a track on which said first transferdevice and said second transfer device are movable, wherein the firstholding unit is arranged on the track and said first transfer devicetranslates on the track between said first holding unit and saidbuilding line and vice-versa, and said second transfer device translateson the track between said first holding unit and said vulcanization lineand vice-versa, wherein said first transfer device is adapted for:transferring the green tyre on the toroidal support from the buildingline to the first holding unit; transferring the toroidal support,separated from the green tyre, from the first holding unit to the coolerof the building line; transferring the toroidal support, separated fromthe green tyre, from the cooler of the building line to a work stationof the building line; and wherein said second transfer device is adaptedfor: transferring the green tyre on the toroidal support from the firstholding unit to a vulcanization unit of the vulcanization line;transferring, after vulcanization, the moulded and vulcanized tyre onthe toroidal support from the vulcanization unit to themounter/dismounter of the vulcanization line; and transferring thetoroidal support, separated from the moulded and vulcanized tyre, fromthe mounter/dismounter of the vulcanization line to the first holdingunit.
 2. The plant for producing tyres for vehicle wheels according toclaim 1, further comprising a second holding unit adapted for holdingthe green tyre and the relevant toroidal support coming out from thebuilding line and for holding the toroidal support, separated from therelevant tyre, coming out from the vulcanization line.
 3. The plant forproducing tyres for vehicle wheels according to claim 2, wherein saidfirst transfer device is adapted for: transferring the green tyre andthe relevant toroidal support from said second holding unit to the firstholding unit; transferring the toroidal support, separated from therelevant tyre, from the first holding unit to the cooling unit of thebuilding line of the production plant; and transferring the toroidalsupport, separated from the respective tyre, from the cooling unit ofthe building line to the second holding unit.
 4. The plant for producingtyres for vehicle wheels according to claim 1, wherein the vulcanizationline comprises two vulcanization units.
 5. The plant for producing tyresfor vehicle wheels according to claim 4, wherein the vulcanization linecomprises two mounters/dismounters.
 6. The plant for producing tyres forvehicle wheels according to claim 5, wherein the building line comprisesfour coolers.
 7. The plant for producing tyres for vehicle wheelsaccording to claim 1, wherein said track extends between the cooler anda work station of the building line.
 8. The plant for producing tyresfor vehicle wheels according to claim 1, wherein said track extendsbetween at least two units selected from a vulcanization unit, amounter/dismounter, a cooler and a second holding unit.
 9. The plant forproducing tyres for vehicle wheels according to claim 8, wherein thetrack extends between the cooler and the second holding unit.
 10. Theplant for producing tyres for vehicle wheels according to claim 8,wherein said track extends between the vulcanization unit and themounter/dismounter.
 11. The plant for producing tyres for vehicle wheelsaccording to claim 1, wherein said track extends between a work stationof the building line and a unit selected from a vulcanization unit, amounter/dismounter, a cooler, and a second holding unit.
 12. The plantfor producing tyres for vehicle wheels according to claim 1, furthercomprising a driver to move the first transfer device and the secondtransfer device along said track.
 13. The plant for producing tyres forvehicle wheels according to claim 1, wherein said vulcanization unitcomprises a vulcanization wheel on which six vulcanization moulds aremounted.
 14. The plant for producing tyres for vehicle wheels accordingto claim 1, wherein said first holding unit comprises two seats forhousing said toroidal support.
 15. The plant for producing tyres forvehicle wheels according to claim 14, wherein said first holding unitcomprises four seats capable of housing said toroidal support.
 16. Theplant for producing tyres for vehicle wheels according to claim 1,wherein said first holding unit is movable.
 17. The plant for producingtyres for vehicle wheels according to claim 1, wherein said firstholding unit is movable along the track.